Re-evaluation of nitrogenase oxygen-protective mechanisms in the planktonic marine cyanobacterium Trichodesmium

There were no apparent differences in distribution of photosystems (PS) I and I1 between central cells and tip cells of trichomes of Trichodesmium thiebautij colonies collected in the eastern Caribbean Sea. Single cell absorption spectra, observations of phycoerythrin fluorescence via epifluorescence microscopy, and enhanced DCMU chlorophyll a fluorescence were essentially identical for both internal and peripheral regions, thus indicating that nitrogenase is not protected from O2 via the absence of PS I1 in the central region of the colony. The calculated DCMU-induced Fluorescence Response Index (FRI) indicates that both central and tip cell areas are similar (FRI range 0.55 to 0.65), and active in photosynthesis Our microelectrode measurements of O2 within and outside of healthy colonies did not indicate a low O2 region in the colony center relative to concentrations at the surface. A theoretical model of oxygen diffusion and respiration in the colony indicated that respiration alone cannot account for the low O2 microzones previously observed by others. The clear sensitivity of T thiebautii nitrogenase to O2 indicates that there must be other, probably intracellular, mechanisms of protecting nitrogenase from O2 inactivation.

[1]  E. Carpenter,et al.  NITROGENASE CONFINED TO RANDOMLY DISTRIBUTED TRICHOMES IN THE MARINE CYANOBACTERIUM TRICHODESMIUM THIEBAUTII 1 , 1991 .

[2]  E. Carpenter,et al.  Hydrogen production and nitrogen fixation by Oscillatoria thiebautii during in situ incubations1,2 , 1987 .

[3]  A. Puppo,et al.  Superoxide dismutase: an essential role in the protection of the nitrogen fixation process? , 1986 .

[4]  T. Saino,et al.  Aerobic nitrogen fixation by the marine non-heterocystous cyanobacterium Trichodesmium (Oscillatoria) spp.: Its protective mechanism against oxygen , 1982 .

[5]  H. Paerl,et al.  Localized Tetrazolium Reduction in Relation to N2 Fixation, CO2 Fixation, and H2 Uptake in Aquatic Filamentous Cyanobacteria , 1982, Applied and Environmental Microbiology.

[6]  I. Bryceson,et al.  Nitrogen fixation in Oscillatoria (Trichodesmium) erythraea in relation to bundle formation and trichome differentiation , 1981 .

[7]  I. Morris,et al.  Physiology of carbon photoassimilation by Oscillatoria thiebautii in the Caribbean Sea1 , 1980 .

[8]  J. Cullen,et al.  Continuous measurement of the DCMU-induced fluorescence response of natural phytoplankton populations , 1979 .

[9]  D. Hall,et al.  Superoxide dismutase and catalase in the protection of the proton-donating systems of nitrogen fixation in the blue-green alga Anabaena cylindrica. , 1978, The Biochemical journal.

[10]  G. Öquist,et al.  A Method for Studying Photosynthetic Capacities of Unicellular Algae Based on in vivo Chlorophyll Fluorescence , 1977 .

[11]  B. B. Jørgensen,et al.  Bacterial sulfate reduction within reduced microniches of oxidized marine sediments , 1977 .

[12]  E. Carpenter,et al.  Marine oscillatoria (Trichodesmium): explanation for aerobic nitrogen fixation without heterocysts. , 1976, Science.

[13]  Y. Fujita,et al.  Phycoerythrin and photosynthesis of the pelagic blue-green alga Trichodesmium thiebautii in the waters of Kuroshio, Japan , 1975 .

[14]  O. Holm‐Hansen,et al.  Nitrogen fixation in the North Pacific Ocean , 1974 .

[15]  K. Anagnostidis,et al.  Modern approach to the classification system of cyanophytes. 3 - Oscillatoriales , 1988 .

[16]  E. Carpenter,et al.  Validity of N2 fixation rate measurements in marine Oscillatoria (Trichodesmium) , 1987 .

[17]  B. Jørgensen,et al.  Microelectrodes: Their Use in Microbial Ecology , 1986 .

[18]  E. Carpenter,et al.  Nitrogen fixation, distribution, and production of Oscillatoria (Trichodesmium) spp. in the western Sargasso and Caribbean Seas1 , 1977 .